To enlarge the coverage area of the system and increase the system capacity, one or more relay stations (RS for short) have been set up between a multi-hop relay base station (MR-BS for short) and a mobile station (MS for short). As shown in FIG. 1, an RS is able to enlarge the coverage area of the system or increase the system capacity by relaying transmissions between an MR-BS and an MS.
At present, resource scheduling of a relaying system can be divided into centralized control and distributed control, wherein the allocation of channel resources in the centralized system must be carried out by the MR-BS, while the RS in the distributed system may allocate part of the resources by itself. Since all resource scheduling in the relaying system using the centralized control are processed by the MR-BS, the corresponding design of hybrid automatic repeat request (HARQ) is more complex.
In the existing technologies, regarding centralized relay of end-to-end HARQ, the superordinate control station has already allocated corresponding feedback channel forwarding acknowledgement (ACK)/negative acknowledgement (NAK) to each RS before the RS sends certain HARQ data. Once an RS receives the data to be forwarded, it is triggered to begin to calculate in which frame the feedback shall start, and then it sends the feedback on the corresponding resources. In the case of transmitting HARQ by downlink data, the feedback sent after an RS delay serves to identify the receiving situation of downlink data in the relay link; in the case of transmitting HARQ by uplink data, the feedback sent after an RS delay is used to identify the receiving situation of uplink data in the relay link.
However, in the existing technologies, there is no uniform feedback method for triggering an RS of the centralized control type to calculate feedback delay in different HARQ application scenarios. For example, in the system shown in FIG. 1, data retransmission may begin at the subordinate node RS2 of RS1. In the case of downlink data retransmission, neither RS1 nor RS2 can receive data to be forwarded, and therefore they will not be triggered to begin to calculate the time delay of forwarding corresponding downlink data feedback. In case of uplink data retransmission, RS1 can not receive data to be forwarded, and therefore it will not be triggered to begin to calculate the time delay of forwarding corresponding uplink feedback. In the existing technologies, the methods of triggering an RS to calculate feedback time delay by downlink data retransmission and by initial data retransmission are different. Moreover, it is not specified how an RS shall process if the uplink feedback fails to be received. Additionally, nor is it specified in the existing technologies how to trigger an RS used for retransmitting data to begin to calculate time delay in the retransmission of uplink data.